Evaporator systems use thermal separation technology and can be used for the concentration or separation of liquid solutions, suspensions and emulsions. During evaporation, a solution is concentrated when a portion of the solvent, usually water, is vaporized, leaving behind concentrate that contains virtually all of the dissolved, suspended or emulsified solids, or solute, from the original feed.
Evaporation is a valuable process technology in a variety of fluid processing industries. For example, evaporation is a valuable process technology in the food, dairy, and beverage industry for concentrating a product (e.g., sugar, milk, proteins, carbohydrates, etc.). Evaporation is also a valuable process in the wastewater treatment industry, particularly where evaporation is considered an alternative process in an increasing number of wastewater treatment applications. It can be effective for concentrating or separating from the solvent salts, heavy metals and a variety of hazardous materials. Also, it may be used to recover useful by-products from a solution, or to concentrate liquid wastes prior to additional treatment and final disposal. Many applications of the technology also produce a reusable water stream, which is a valuable feature where water conservation is a priority or mandated by local regulations and laws.
A drawback of traditional evaporator systems is that they can constitute a significant capital investment that many businesses may not be able to afford. Depending on the capacity required by a process or application, the size of an evaporator system can be large, requiring substantial capital investment to purchase the equipment and for the facility to house the equipment, including ancillary equipment (e.g., feed tanks, heaters, cleaning systems, etc.), and installation (e.g., foundations, structural support steel, piping, electrical, etc.). Therefore, there is a need to improve the technology to make it more compact and affordable.
In response to this need, in 2011, Caloris Engineering, LLC (“Caloris”) introduced the CC1 Concentrix compact mechanical vapor recompression (MVR) evaporator system. Subsequently, in 2013, Caloris introduced the CC2 Concentrix compact MVR evaporator system. The CC1 and CC2 (collectively “first generation CC” systems) were designed and engineered to offer the high overall energy efficiency of falling film MVR evaporators in a compact design.
Falling film evaporators utilize a vertical tube and shell heat exchanger to heat the mass of a liquid flowing downward via gravity inside the tubes by transfer of thermal energy through the tube wall from the condensation of vapors on the outside of the tube wall. Typically, an induced draft at the lower end of the heat exchanger bundle promotes the flow of evaporated vapors co-current with the liquid vertically down the inside of the tubes. As the liquid and vapor exit the tubes at the lower end of the tube bundle, the liquid continues to fall under gravity downward into a liquid sump, while the vapor is drawn away from the liquid phase by the induced draft.
A variety of mechanical recompression devices (e.g., turbofan, rotary compressor, etc.) can be used to induce the draft of evaporated vapors from the bottom of the tube bundle. A separation chamber can be used to supplement the separation of entrained liquid droplets from the vapor flow prior to the mechanical recompression device. Mechanical compression of the vapors in the mechanical recompression device increases the temperature of those vapors. The discharge flow of vapors from the mechanical compression device can then be directed into the shell of the heat exchanger bundle, where those vapors then condense on the outside of the tubes transferring thermal energy to the liquid inside the tubes. The liquid phase of condensed vapors on the outside of the tubes flows to the bottom of the tubes via gravity, for removal and collection separate from the concentrated liquid stream.
One aspect of the first generation CC systems, which contributed to the high overall energy efficiency compared to that of existing falling film evaporator systems, was the configuration of the falling film heat exchanger and the vapor separator as one common assembly. Specifically, the first generation CC design comprised the falling film heat exchanger bundle as a larger cylinder around the outside walls of the central cylindrical vapor separator body. The vertical cylinder walls of the vapor separator also served as the inside cylinder wall of the heat exchanger bundle. In addition, the lower portion of the vapor separator was open fully 360° around its circumference to the space directly beneath the falling film heat exchanger bundle. This allowed vapor flowing out of the inside of the heat exchanger tubes at the bottom of the exchanger bundle to be drawn horizontally inward into the vapor separator chamber without the need for interconnecting duct work.
Due to the flow of evaporated vapors into the bottom of the vapor separator cylinder from all sides 360° around its circumference, the vapor separator for the first generation CC systems was configured as a gravity separator, requiring that the cylinder diameter of the chamber be specified to achieve a vapor flow rise velocity inside the vapor separator vessel at a rate sufficiently low enough to allow a portion of the entrained liquid droplets in the vapor flow to fall via gravity downward in counter flow to the rising vapor flow created from the induced draft of the mechanical vapor recompression device, with the liquid droplets falling into a liquid collection sump directly beneath the separator cylinder.
At the top of the vapor separator cylinder was a ceiling wall surface, which connects to the inner wall of the cylinder, and had a circular opening at the center of the ceiling through which evaporated vapors rising vertically up through the cylinder passed. Directly beneath and connected to the circular hole in the ceiling was a transition section of a conical or similar rounded shape that was of smaller diameter at its top than at its bottom, which served to direct the flow of vapors from the outer portions of the upper cylinder volume toward the circular opening in the ceiling.
Mounted directly above the circular opening in the ceiling was a traditional turbofan impeller wheel, supported on a vertical shaft in a horizontal orientation with the vertical centerline of the cylinder. The diameter of the circular opening in the ceiling of the vapor separator was specified to be somewhat smaller than the diameter of the turbofan impeller wheel, allowing the flow of vapor passing through the ceiling's circular opening to enter at a perpendicular angle into the center of the turbofan impeller wheel. By spinning the turbofan impeller wheel, the surfaces of the impeller wheel mechanically displaced the vapors that were drawn into the center of the impeller wheel, causing those vapors to be pushed radially outward 360° in a horizontal plane from the outer perimeter of the spinning impeller wheel.
Mounted in a horizontal orientation around the outer circumference of the turbofan impeller wheel was a radial diffuser functioning as the mechanical recompression device, which achieved compression of the vapors being pushed radially outward 360° from the spinning turbofan impeller wheel by mechanically imposing backpressure on the vapors, similar to the compression of vapors that is more commonly achieved using a traditional scroll housing around a turbofan impeller wheel. Traditional scroll turbofan housings fully enclose the impeller and a discharge nozzle in the outer perimeter of the scroll housing can direct the discharge flow of vapor through ductwork to the shell of the heat exchanger. Instead, the radial diffuser of the CC system allowed the vapor to continue flowing radially outward 360° generally in a horizontal plane from the outer edge of the rotating impeller wheel and through the diffuser body, with the internal vanes of the radial diffuser compressing the vapor as it passed through the radial diffuser. The radial diffuser design directed the compressed vapor directly into the shell of the evaporator's falling film heat exchanger surrounding the vapor separator vessel 360° around its circumference. This design required no ductwork to interconnect the vapor outlet of the vapor separator and the suction inlet of the turbofan impeller. A nominal length of a straight ductwork channel may have been used between the outer edge of the radial diffuser body and the inner cylinder walls of the heat exchanger shell.
The present disclosure provides and describes a second generation Concentrix evaporator system, which is an improved design of the first generation CC. According to the embodiments of the present disclosure, this includes enhanced performance of the vapor separator by increased separation of entrained droplets within the vapor separator while maintaining a common vessel of limited diameter such that it is still capable of transportation over public roads.
It is understood that the use of a compact MVR evaporator system of the present disclosure is not limited in its application. The compact MVR evaporator system of the disclosure can be used in a variety of applications, for example, concentration of food and beverage products (e.g., sugars, juices, jellies, purees, pectin, brewer's yeast, beer dealcoholization, beer wort, stillage, coffee, gelatin, mash, starch, yeast extract, dairy products); processing spent liquids in the pharmaceutical and life science industries; concentration of select chemicals; wastewater from chemical processes; metal surface treatment effluent; food processing waste streams; recovering oil and water from emulsions from metal processing operations and foundries used in the automotive industries; concentration of wastewater from dye operations; cleaning waste streams (from component cleaning, tank cleaning, polishing and pretreatment cleaning); recover water from industrial laundries wastewater, boiler and cooling tower blow down; to name just a few.